Maura schiavocampo, ABC news, New York. A new hit from the airlines. First, it was frequent flyer miles. Then, bereavement fares. Tonight, a crackdown on the size of our carry-on bags. The latest salvo in the battle between airlines and passengers, especially passengers trying to carry their bags onboard. David Kerley told under the circumstances what happened today. Reporter: You've seen it. Fliers trying to avoid the baggage fees. We want to welcome travelers with carry-ons that have no chance of fitting in the overhead compartment. Reporter: Like in this skit on "Saturday night live." Those flyers may be stopped before they get to the gate and sent back to the counter. American airlines are looking for folks who may be carrying too much. United has recently added sizing kiosks at airports. The airline says this is about loading and unloading quickly. This is not a new policy. This is just enforcement of the rules. Reminding customers about the limits and size of bags they can bring onboard. Passengers will not have to go back to the counter. But they have to gate-check without paying that bag fee. Tonight, the bag police are on the job. Meaning there may be a little more room in the overhead compartments. David Kerley, ABC news, Washington, Reagan airport.

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